AGM Battery Recharging

mrb2222 · #1 (**permalink**) 02-18-2003

I like the idea of AGM batteries in my boat but I don''t know much about charging them. Is a 3 stage charger the best? What kind of alternator is best? Any thoughts? Thanks

Denr · #2 (**permalink**) 02-19-2003

I plan to purchase a couple group 31s AGMs for my wind jammer this season. According to the information I''ve read, the AGMs can be charged with multi-stage chargers, the voltage setting should be in the wet cell position.The manbufacturer East Penn has some competitive prices, under $150 ea. for the 31s.

mrb2222 · #3 (**permalink**) 02-19-2003

Thanks for the charging info.
Batteryweb.com has Concorde grp 31''s for about $200 including delivery. This battery has gotten some very good press.

lecomte38 · #4 (**permalink**) 02-19-2003

The volt regulator should NOT be set to wet cell. gel cells/agm must be charged at a lower voltage and temperature monitored/regulated. much more info at: www.eastpenn-deka.com

I just posted this on another BB. Save your money and buy good old lead acid golf cart batteries for less then half the price. abuse em, boil em, kill em dead. add water once a year. Trojan T105s rule !!!

Trojan Man

Denr · #5 (**permalink**) 02-19-2003

Wrong Trojan Breath. It is the wet cells and the AGMs that are charged alike, the gels are charged at a lower voltage.

Denr · #6 (**permalink**) 02-19-2003

More information and I quote:

Your LIFELINE charger is suitable for immediate installation with either LIFELINE Advanced AGM or regular flooded batteries. When installing a LIFELINE charger with Gel batteries the Equalize/Fast Charge setting must be reduced prior to it''s use or damage to the batteries will result!

lecomte38 · #7 (**permalink**) 02-25-2003

denr - did you bother to go to the deka eastpenn manufactures web site and read about VRLA batteries?

"It is critical that a charger be used that limits voltage. The charger must be temperature-compensated to prevent under or overcharging due to ambient temperature changes." ( from page 2 of technical manual for Valve-Regulated Lead-Acid (VRLA) gelled electrolyte(gel) and Absorbed Glass Mat(AGM) batteries )

www.eastpenn-deka.com

tsenator · #8 (**permalink**) 02-25-2003

I hate to back up denr on this one, but I think it really depends on what the charger is set for. There are many variations of outputs and configurations for chargers. Some of the good 3-stage marine chargers are typically automatically set-able for either AGM/Wet/Gell with a dipswitch (like the Xantrex Truecharger 20/40 http://www.xantrex.com/support/docserve.asp?id=462 ) or (I think manually)adjustable like the LIFELINE (http://www.lifelinebatteries.com/aboutchargers.htm) "LIFELINE chargers provide fully adjustable float and equalize Voltage settings for all types of batteries operating at any temperature" So they must be set-up for the correct use. But they can be set up to well within the voltage limits of AGM batteries. As I see the specs from deka eastpenn the max allowable voltage between about 80-100deg is about 14.3 and 14.4 volts.

But to allude to having the settings the same for both Wet and AGM is not correct, UNLESS you have a charger that doesn''t not exceed the AGM voltages ......it''ll work fine for WET, but sometimes the Wet batteries like to get a few tenths higher voltage at the absorption phase. (http://www.uuhome.de/william.darden/dcfaq6.htm)

Plus you really don''t want to equalize an AGM like you do to a Wet cell.

ps I hate that the deka eastpenn website mandates that I have to give them all my particulars just get get info for their products!

tsenator · #9 (**permalink**) 02-25-2003

Oh...I just re-read and saw that denr said AGM''s and Wet cells are charged alike. No not really. Not for optimal charging. Take a look here.

http://www.uuhome.de/william.darden/dcfaq6.htm

But that doesn''t mean you can''t set your output to never go above 14.3 v @ 80deg F and have it charging both a wet Cell and an AGM. You can but, 14.3 is not optimal for a typical Wet Cell and 14.3 is at the high side for the typical AGM. (Just don''t equalize the AGM you''ll "boil" it)

What I do on my boat is have my charger charging the Wet cells (@ about 14.5 V max in the absorption phase) and then I have an echo charger to feed the charge to the AGM I have as my starting battery at about 14.3V max. This works out great because it looks like my echo charger has about a .1-.2 volt drop when feeding my AGM starting battery and never exceeds that limit.

BTW, the reason they have the limits on the AGM is because they don''t want it to "boil" because once it gets "boiled" there is no replenishing of the electrolyte, like there is with a wet cell, so if you do boil it, then its done for. Its a built in safety factor they have .